Pump impeller and radial pump comprising the impeller

ABSTRACT

The invention relates to a pump impeller for a radial pump with a carrier plate comprising an intake side and a rear side situated opposite the intake side, a blading being provided on the intake side for conveying a medium to be pumped, characterized in that, on the rear side of the carrier plate, at least one flow profile is situated which is configured and formed to reduce at least a difference between a pressure-induced balance of forces on the carrier plate and on a cover plate in the case of a rotation of the pump impeller in a rotational direction (DR).

CLAIM FOR PRIORITY

This application claims the benefit of priority of German ApplicationNo. 10 2020 131 524.4, filed 27 Nov. 2020, which is hereby incorporatedby reference in its entirety.

TECHNICAL FIELD

Embodiments of the invention relate to a pump impeller and to a radialpump comprising the impeller.

BACKGROUND

Impellers for radial pumps from the prior art comprise a carrier plate,which comprises towards an intake side a blading provided for conveyinga fluid to be pumped. Optionally, a pump impeller of this type iscovered with a cover plate on the intake side. During operation of animpeller of this type, a pressure difference occurs between the intakeside, i.e., on the side of the blading as seen from the carrier plate,and a rear side, since fluid to be pumped is conveyed radially outwardsby the rotation of the impeller, in such a way that a suction areaoccurs radially inwards. An axial force thus occurs at the impeller as aresult of the difference between the pressure-induced balance of forceson the carrier plate and on the cover plate. The axial force has to beabsorbed or braced by suitably formed axial bearing systems. Axialbearings of this type therefore have to be dimensioned, formed andconstituted in such a way that they can reliably receive the axialforces over the service life of the radial pump.

SUMMARY/OVERVIEW

An aspect of embodiments according to the invention is to specify a pumpimpeller by means of which pressure-induced axial forces acting towardsthe suction mouth of the impeller can be reduced without significantlydetracting from an internal efficiency of the pump impeller or of theradial pump comprising the pump impeller.

A pump impeller of this type should additionally be producible in asimple manner, without any particular additional complexity over theproduction of a prior art pump impeller.

Another aspect of embodiments according to the invention is to specify aradial pump which generates, as regards the pump impeller, lower axialforces which have to be braced/absorbed in the interior of the radialpump.

A further aspect of embodiments according to the invention is to specifya radial pump which can be produced cost-efficiently overall and ends upless complex as regards the axial bearing system of a drive shaft/of thepump impeller.

The above aspect as regards the pump impeller is achieved by a pumpimpeller having the features according to embodiments of the invention.Advantageous embodiments are specified in the dependent claims.

As regards the radial pump, the aspects are achieved by a radial pumphaving the features according to embodiments of the invention.

In the context of the following description, the influence on thebalance of forces at the impeller from the flow profiles is sometimesreferred to for simplicity as a “negative pressure” in the area of thecarrier plate rear side.

According to embodiments of the invention, the pump impeller for aradial pump with a carrier plate comprises an intake side and a rearside situated opposite the intake side, a blading being provided on theintake side for conveying a medium to be pumped, wherein, on the rearside of the carrier plate, at least one flow profile is situated whichis configured and formed to reduce at least a difference between apressure-induced balance of forces on the carrier plate and on a coverplate in the case of a rotation of the pump impeller in a rotationaldirection DR.

In a pump impeller according to embodiments of the invention, it isparticularly advantageous that a rear-side contouring of the carrierplate of the impeller reduces an axial force at the impeller, due to adifference in the pressure-induced balance of forces on the carrierplate and on the cover plate, during the operation of the impellerwheel, i.e., in dynamic use within a pump fluid. This takes place by wayof a dynamic flow around the at least one flow profile. As a result ofthe rotational movement of the impeller, the fluid to be pumped whichsurrounds the flow profiles, the profiles and the cut-off edges flowsover the flow profile(s), resulting in separation of the flow behind thecut-off edges. The rise in the flow profiles is orientated counter tothe rotational direction DR of the impeller, meaning that nearby fluidto be pumped migrates along the flow profile, for example towards thecut-off edge, as the impeller rotates. The separation of the flow at thecut-off edge brings about a fall in pressure after the flow profile,which reduces the total static pressure distribution in a sealing gapbetween the pump impeller and a pump housing. This changes thepressure-dependent balance of forces on the pump impeller, and theresulting axial thrust (the axial resultant force of the static pressurebalance over the impeller geometry) orientated towards the suction area(the suction mouth) is reduced. Flowing over the flow profile also doesnot cause a significant dynamic pressure, such as occurs, by contrast,in a blade with a rectangular profile for example, and this additionallyinfluences the pressure level. In this case, an influence on thepressure level means a reduction in the static pressure distribution inthe rear side space of the wheel, in other words the pressuredistribution on the carrier plate rear side. This results in a lowerresultant axial force towards the suction mouth.

Thus, embodiments of the invention take the approach of specifying apump impeller and a radial pump comprising the pump impeller wherein itis possible to provide a reduction in the static pressure distributionon the rear side of the carrier plate and thus to achieve an influenceon the balance of the forces acting on the pump impeller. In particular,the static pressure distribution at the rear side of the carrier ischanged, or reduced in total over all of the forces, in such a way thatthe balance of forces is influenced.

Embodiments of the invention thus manage to reduce the resultant axialthrust at the impeller in a targeted manner. This results in relief forthe bearing system in the axial direction, potentially leading to asaving on costs and to constructional simplification in the selectionand design of the axial bearing. The flow profile, in other words forexample the ramp profile structures, may be made use of both inmechanical and in electrical pumps. Because no undercutting contours areapplied on the rear side of the carrier plate, production by injectionmoulding can be implemented in a simple manner, without a slide, in anappropriate injection-moulding tool.

The relatively low dynamic pressure, generated for example over the flatflow profiles, also only leads to an extremely small loss of efficiencyin the pump impeller or in a fluid pump comprising the pump impeller.

In a preferred embodiment of the invention, the at least one flowprofile, as seen in a circumferential direction UR, is a ramp contour,in particular a short ramp contour, i.e., a ramp ridge, or a long rampcontour, i.e., a circular surface segment ramp.

Ramp contours have proven expedient in generating the negative pressure;in particular, ramp-ridge-like short ramp contours or a long rampcontour, i.e. ramps with circular surface segment ramp surfaces, areconceivable. In the case of a short ramp contour, in which an uninclinedsubsurface of the rear side face of the carrier plate is present betweentwo ramp ridges which are adjacent in the circumferential direction UR,the effect according to embodiments of the invention is alreadypronounced, but occurs in a locally concentrated manner in the area ofthe ramp rear surfaces, which are relatively short in thecircumferential direction UR, of the ramp ridges.

If the flow profiles are formed as a long ramp contour, a singleinclined ramp rear surface is provided between two cut-off edges ofadjacent ramps, and is a circular surface segment. In other words, inthe case of a long ramp contour, the surface between two cut-off edgesis fully inclined with respect to a plane of the rear side of thecarrier disc, whereas a short ramp, by contrast, has an inclined ramprear surface and an uninclined subsurface of the rear side of thecarrier plate between two cut-off edges.

In the case of a long ramp structure, the negative pressure distributionis present over a larger area on the rear side of the pump impeller, andthe total negative pressure is greater in magnitude.

In a further preferred embodiment of the invention, n ramp contours aredistributed over a circumference U of the pump impeller, n preferablybeing ≥2, particularly preferably n≥4, more preferably n≥6.

With an increasing number of ramp contours on the rear side of the pumpimpeller, it has been possible to establish, as a basic principle, adecreasing pressure difference and also a more uniform pressuredistribution over the rear side of the pump impeller. So as to meetacoustic demands to a particular degree, it has proven expedient toselect an integer multiple of the number of blades of the pump impellerfor the number of ramp contours on the rear side of the pump impeller.

In a further embodiment of the pump impeller according to the invention,the at least one ramp contour is formed raised up from a base surface ofthe rear side counter to the rotational direction DR.

Alternatively, it may be provided that the at least one ramp contour(cut-off edge) is flush with respect to the base surface of the rearside and that intervals between two ramp contours (cut-off edges) areformed recessed with respect to the base surface.

Aside from the above-described raised ramp contours and/or the sunkcut-off edges with a ramp contour flush with the annular edge, it isnaturally also possible to form the ramp contours only partially sunk,in such a way that a cut-off edge raised with respect to a base surfaceis present and at least one sub-area between two adjacent ramp contoursis sunk with respect to the base surface.

In a further embodiment of the pump impeller according to the invention,the at least one ramp contour is formed raised with respect to the basesurface of the rear side, and at least part of the intervals between tworamp contours is formed recessed with respect to the base surface.

In a further embodiment of the pump impeller, the ramp contour has acut-off edge which extends in particular radially.

In the case of a radially progressing extension of the cut-off edge, inparticular progressing radially in a straight line in the manner ofspokes, it has been possible to observe a particularly high negativepressure development.

In a further embodiment of the pump impeller according to the invention,a maximum height h of the ramp contour is smaller than a wall thicknesst of the carrier disc.

According to embodiments of the invention, it has been recognised thateven a relatively small ramp height h, which may be smaller than thewall thickness of the carrier disc, is sufficient to achieve a goodcompromise between the achievable negative pressure and the loss ofefficiency to be accepted.

In a further embodiment of the present invention, a radial extension ofthe cut-off edge extends from a hub area of the pump impeller to aradially outward circumferential annular edge of the base surface.

The radial extension of the cut-off edges is advantageously not taken asfar as the outermost circumferential edge of the carrier plate of thepump impeller, so as not to generate any additional flow cut-offs oreddies there with flows occurring at the end of the opposite pumpblading, potentially leading to an undesirable reduction in efficiency.Therefore, an annular ring is left on the rear side of the carrier plateof the pump impeller, and leaves a distance from the circumferentialedge of the carrier plate.

In a further preferred embodiment, a ramp rear surface of the at leastone ramp contour is a plane.

A ramp rear surface in the form of a plane constitutes a particularlysimple three-dimensional shape and can in particular be implemented in asimple manner in a production tool.

In a further particular embodiment, the ramp rear surface, as seen inthe circumferential direction UR, is formed curved, and the curvature isformed constant along the circumferential direction UR or increasingtowards the cut-off edge.

As a result of the curved formation of the ramp rear surface,localisation of the negative pressure foci can be influenced for eachramp in a targeted manner.

In a further preferred embodiment of the invention, the cut-off edgedescends perpendicular to the base surface.

In another embodiment, the cut-off edge descends perpendicular to theramp rear surface or, in the case of a curved formation of the ramp rearsurface, descends perpendicular to a tangent plane to the ramp rearsurface in the area of the cut-off edge.

A descent of the cut-off edge perpendicular to the base surface, i.e.,either to the plane of the carrier plate rear side or to theplane/tangent plane of the ramp rear surface, in particular withoutundercutting, ensures a configuration free of undercuts, facilitatingimplementation in the tool.

In a second aspect of the invention, a radial pump comprises a pumpimpeller in accordance with one of the aforementioned embodiments.

For the radial pump according to the invention, the aforementionedadvantages can be anticipated if a pump impeller according to theinvention is used.

BRIEF DESCRIPTION OF THE FIGURES

In the following, embodiments of the invention are described in greaterdetail by way of example with reference to the drawings, in which:

FIG. 1 is a perspective view of a rear side of a pump impeller accordingto embodiments of the invention;

FIG. 2 is a perspective drawing of a cut-out representation of arear-side flow profile in the formation of a ramp;

FIG. 3 schematically shows a comparison of a negative pressuredistribution on the rear side of a pump impeller without rear-sidecontouring (left), with seven short ramp contours (centre), and with sixlong ramp contours (right);

FIG. 4 schematically shows part of a radial pump according toembodiments of the invention comprising the impeller, in a longitudinalsection.

DETAILED DESCRIPTION

FIG. 1 is a perspective view towards a rear side 2 of an embodiment ofthe pump impeller 1 according to embodiments of the invention. Oppositethe rear side is an intake side 3 of the pump impeller 1. The rear side2 is formed by a carrier plate 4. On the intake side 3 of the carrierplate 4 is a blading 5. To the intake side, the blading 5 is followed bya cover plate 6. Flow ducts 7 are formed between the carrier plate 4 andthe cover plate 6, and are respectively delimited in a circumferentialdirection UR by blades of the blading 5. In an axial direction AR, theflow ducts 7 are delimited by the carrier plate 4 and the cover plate 6.An intake opening (not shown) for fluid to be pumped is aligned with theaxial direction AR, which in FIG. 1 is coincident with the axis ofrotation of the pump impeller 1 on the intake side 3 of the pumpimpeller 1.

In FIG. 1, a schematically shown hub area 8 is positioned centrally onthe middle of the rear side 2 of the carrier plate 4. The rear side 2has an annular edge 9 outward in a radial direction R. Between the hubarea 8 and the annular edge 9 in the radial direction R, a plurality offlow profiles 10 are situated on the rear side 2 of the pump impeller 1.In the embodiment of FIG. 1, the flow profiles 10 are formed as rampcontours 11.

In a plan view, a ramp contour 11 has a circle-segment-shaped ramp rearsurface 12. The ramp rear surface 12 is situated inclined at an angle α(cf. FIG. 2) to a base surface 13 forming the rear side 2, and has acut-off edge 14 as seen counter to a rotational direction DR. Thecut-off edge 14 is orientated approximately parallel to the axialdirection AR, and forms a step 15 of height h (cf. FIG. 2). The step 15is raised with respect to the base surface 13 by the magnitude of theheight h. Following a cut-off edge 14 counter to the rotationaldirection DR, the ramp rear surface 12 of the following ramp contour 11joins on seamlessly. In the axial direction AR, in this joining area,the ramp rear surface 12 is approximately flush with the base surface 13and rises at the angle α.

In the embodiment of FIG. 1, in total six ramp contours 11, each of thesame area size (in a plan view), are situated distributed over thecircumference U of the rear side 2. In total, six cut-off edges 14 thusoccur. The cut-off edges 14 are arranged proceeding from the hub area 8radially in a spoke shape, and have an angle β of 60° between them ineach case. Naturally, in a modification to FIG. 1, the number of cut-offedges 14 and/or associated ramp contours 11 may be lower or higher thansix. A number n=6 has proven particularly expedient.

In the context of modifications to embodiments of the invention, it isalso possible to configure the individual ramp contours 11 differentlysized in the circumferential direction UR. Thus, for example, a rampcontour 11 having a larger angle β, for example having the angle β=80°,may be followed by a ramp contour 11 having a smaller angle (for exampleβ=40°), and differently sized ramp contours 11 of this type may followone another alternately.

In the selection of the segment size (angle β) of the ramps, it isimportant to have as uniform a distribution as possible over thecircumference U, in such a way that no imbalances occur.

So as to keep the efficiency reduction due to increased flow resistanceat the rear side 2 of the pump impeller 1 within the tightest possiblelimits, it is advisable to select a height h of the step 15 less than orequal to a thickness t of the carrier plate 4. In the embodiment, bycomparison with the thickness t, the height h is about half of thethickness t.

FIG. 2 shows a ramp contour 11 cut away in an enlarged cut-out. The rampcontour 11 of FIG. 2 is a ramp contour 11 such as was described inconnection with FIG. 1. The ramp rear surface 12 iscircle-segment-shaped in a plan view, and rises from the level of thebase surface 13 linearly at the angle α. The ramp rear surface 12 ofthis embodiment is thus an inclined plane with respect to the basesurface 13.

Equally, it is of course possible to form the ramp rear surface 12 notas a plane but rather as a curved ramp rear surface 12, which rises, forexample in a uniformly curved manner, by the height h from the level ofthe base surface 13 to the cut-off edge 14. In addition, it is possiblefor the curvature along the circumferential direction UR as far as thecut-off edge 14 not to be uniform, but rather for a lower curvatureinitially to be present and for the curvature to increase towards thecut-off edge 14.

FIG. 3 shows in total three rear sides 2 of pump impellers 1. On the farleft of FIG. 3, a pump impeller 1 from the prior art without flowprofiles 10 on the rear side 2 is shown. In the embodiment of FIG. 3(centre), the pump impeller 1 has in total seven ramp ridges 20uniformly distributed in the circumferential direction UR as flowprofiles. The ramp ridges 20 likewise have cut-off edges 14. By contrastwith the above-described ramp contours 11 (long ramp contours) of theembodiments of FIGS. 1 and 2, ramp ridges 20 differ from theabove-described ramp contours 11 (long ramp contours) in that a cut-offedge 14 of a ramp ridge 20 is initially followed in the rotationaldirection DR by a circle segment surface, which is positioned on thevertical level in the axial direction AR of the base surface 13 and isnot inclined with respect to the base surface 13.

In a plan view, the ramp ridge 20 is formed rectangular with a width b,within which the ramp rear surface 12 rises from the level of the basesurface 13 by the height h. Ramp ridges 20 of this type constitutespoke-shaped local elevations. In particular in the area of the rampridges 20, i.e., in particular in the region downstream from the cut-offedges 14 counter to the rotational direction DR, a negative pressureoccurs locally when the pump impeller 1 is driven in the rotationaldirection DR. This is indicated in FIG. 3 (centre) by the darker shadingin the area of the radial centre of the ramp ridges 20.

The embodiment of FIG. 3 (right) corresponds to the above-describedembodiment of FIG. 1, 2, and has in total six ramp contours 11, which asdescribed above are circle-segment-shaped in a plan view and rise from acut-off edge 14, leading in the rotational direction DR, of the rampcontour 11 to the cut-off edge 14, trailing in the rotational directionDR, of the ramp rear surface 12.

FIG. 3 (right) illustrates that, with this type of rear-side contouringof a pump impeller 1 according to embodiments of the invention, anegative pressure that is overall greater and also higher in magnitudecan be achieved by comparison with the embodiment in FIG. 3 (centre) andby comparison with the embodiment in FIG. 3 (left) (prior art). Theincreased negative pressure formation (in FIG. 3, right) is marked withdarker hatching in the vicinity U of the cut-off edges 14.

In tests, the highest negative pressure values, and thus the highestaxial force relief of the corresponding axial bearings of the pump, werebrought about with the contouring of FIGS. 1 and 2.

The pump impeller 1 sits on a drive shaft 101, which can be motor-drivenin the rotational direction DR. The radial pump 100 has a pump housing102, which forms a pump chamber 103. The pump impeller 1 sits in thepump chamber 103. The carrier plate 4 forms, with a rear wall 104 of thepump housing 102, a gap 105 in which fluid to be pumped is present. Theflow profiles 10 are situated on the rear side 2 of the carrier plate 4.In FIG. 4, the flow ducts 7 are delimited axially to the left by thecover plate 6. In FIG. 4, the fluid to be pumped flows from left toright, flows through the flow ducts 7, and arrives outside through anoutlet duct 106. The flow direction of the fluid to be pumped isindicated by arrows 107.

LIST OF REFERENCE NUMERALS

1 Pump impeller

2 Rear side

3 Intake side

4 Carrier plate

5 Blading

6 Cover plate

7 Flow ducts

8 Hub area

9 Annular edge

10 Flow profile

11 Ramp contour

12 Ramp rear surface

13 Base surface

14 Cut-off edge

15 Step

20 Ramp ridge

100 Radial pump

101 Drive shaft

102 Pump housing

103 Pump chamber

104 Rear wall

105 Gap

106 Outlet duct

107 Arrows

AR Axial direction

DR Rotational direction

R Radial direction

UR Circumferential direction

U Circumference

b Width

h Height

t Wall thickness

n Number

α Angle

β Angle

What is claimed is:
 1. A pump impeller for a radial pump with a carrier plate comprising: an intake side and a rear side situated opposite the intake side, a blading being provided on the intake side for conveying a medium to be pumped, wherein, on the rear side of the carrier plate, at least one flow profile is situated which is configured and formed to reduce at least a difference between a pressure-induced balance of forces on the carrier plate and on a cover plate in the case of a rotation of the pump impeller in a rotational direction (DR).
 2. The pump impeller according to claim 1, wherein the at least one flow profile, as seen in a circumferential direction (UR), is a ramp contour, in particular a short ramp contour, i.e., a ramp ridge, or a long ramp contour, i.e., a circular surface segment ramp.
 3. The pump impeller according to claim 1, wherein n ramp contours are distributed over a circumference (U) of the pump impeller, n being ≥2.
 4. The pump impeller according to claim 1, wherein in an, as seen in a radial direction (R), internal area of the rear side of the carrier plate, the number (n) of the ramp contours is lower than in an area further outside, which has a higher number (n) of ramp contours, in particular an integer multiple of the number (n), in particular in that six ramp contours are provided in the inner area and twelve ramp contours are provided in the outer area (closer to the annular edge).
 5. The pump impeller according to claim 1, wherein the at least one ramp contour is formed raised from a base surface of the rear side counter to the rotational direction (DR).
 6. The pump impeller according to claim 1, wherein the at least one ramp contour is flush with respect to the base surface of the rear side counter to the rotational direction (DR) and intervals between two ramp contours are formed recessed with respect to the base surface.
 7. The pump impeller according to claim 1, wherein the at least one ramp contour is formed raised with respect to the base surface of the rear side, and at least part of the intervals between two ramp contours is formed recessed with respect to the base surface.
 8. The pump impeller according to claim 1, wherein the ramp contour has a cut-off edge which extends in particular radially.
 9. The pump impeller according to claim 1, wherein a maximum height (h) of the ramp contour is smaller than a wall thickness (t) of the carrier plate.
 10. The pump impeller according to claim 1, wherein a radial extension of the cut-off edge extends from a hub area of the pump impeller to a radially outward circumferential annular edge of the base surface.
 11. The pump impeller according to claim 1, wherein in that a ramp rear surface of the at least one ramp contour is a plane.
 12. The pump impeller according to claim 9, wherein the ramp rear surface, as seen in the circumferential direction (UR), is formed curved, and the curvature is formed constant along the circumferential direction (UR) or increasing towards the cut-off edge.
 13. The pump impeller according to claim 1, wherein the cut-off edge descends perpendicular to the base surface.
 14. The pump impeller according to claim 1, wherein the cut-off edge descends perpendicular to the ramp rear surface or, in the case of a curved formation of the ramp rear surface, descends perpendicular to a tangent plane to the ramp rear surface in the area of the cut-off edge.
 15. A radial pump comprising a pump impeller according to claim
 1. 